After manufacture, many parts and components require additional finishing work to further enhance the surface finish of the parts. Examples of this include removing imperfections from a subtractive manufacturing process, (e.g. CNC or other machine burrs and imperfections, caused by a variety of cutting methods; parting line and other flash from molding or forming, etc.). The industry uses a number of generally accepted techniques for polishing or finishing these parts, to remove burrs and mold flash, etc. that include vibratory bowls, tumbling operations, blasting with different types of traditional media (e.g. plastic pellet, steel, shot, soda ash, abrasives, etc.). Further desirable finishing attributes may include surface finish, surface color, surface texture, surface cleanliness, etc. Consequently, the finishing work can be applicable to parts that are manufactured using additive techniques (e.g. 3D printing.)
One known technique used in this finishing work involves the processing of a batch of parts with traditional media that is recovered and reused (for continual blasting in an automated fashion) while the parts are in a frozen state in a chamber that is cooled with liquid nitrogen. This is generally referred to “Cryogenic Deflashing and/or Deburring”. The parts may be placed in a perforated drum which itself is rotated about an axis. The parts to be treated and the traditional media which will treat these parts may be placed in the rotating drum. The interaction of the traditional media and the parts will act to remove burrs, flash, etc. The traditional media may be of a type that can be recycled and reused during the process, but a problem with this technique is that the parts, once processed, will likely need to be “cleaned” to remove all traces of the traditional media which may be harmful to the parts after processing. Since the traditional media itself may be very much smaller than the parts, traces may remain after the process has been completed. A number of companies produce such devices, including in no special order of presentation: C.D.S. Inc, C S P Cryomatic and Leonard Enterprises, Inc.
Another technique that is occasionally used involves the manual blasting of individual parts with a stream of dry ice particles to remove undesired characteristics of the part, such as burrs or flash, as mentioned above. In this technique, the part and the dry ice delivery systems are manipulated so that the spray pattern of dry ice is presented to the areas of the part that require the finishing process. This is generally referred to as “Dry Ice Blasting/Blast Cleaning or CO2 Cleaning/Blasting”. Machines are commercially available which will present dry ice particles that are generally propelled by compressed air and are then “blasted” against a part. A similar technique shoots CO2 liquid (or gas) through a suitable nozzle system to cause the CO2 to change state and solidify so that it is projected (or shot) at the parts to be treated. One downside of this technique is that it is not suitable for large scale (or batch) processing of parts. A number of companies already manufacture and distribute such “ice blasting” devices, including Cold Jet, LLC which utilizes dry ice as the delivery medium and Cool Clean Technologies, LLC which utilizes a tank of liquid CO2 as the delivery medium.
There are “pros” and “cons” to each of the foregoing methods. These include, in connection with the cryogenic deflashing technique:
Pros                Batch processing of parts.        Computer programmed to eliminate human variables.        Deburring/deflashing can be accomplished on almost all materials due to the cryogenic temperature inside the parts chamber that support the achievement of glass transition temperature (Tg) for effective deburring/deflashing.        
Cons                Uses traditional media which can become trapped in the geometry of parts.        Exposes parts to traditional media that may bring undesirable reactions/potential reactions (e.g. PBA).        Traditional media is often attracted to the part surfaces via ESD, water tension or other mechanisms resulting in parts that are “contaminated” with residual media.        Traditional media can be abrasive and damage thin surface or fragile partsFor the dry ice blasting technique, the “pros” and “cons” are as follows:Pros        Uses dry ice that is considered to be a non-abrasive media        Dry Ice sublimates without leaving any residual media        Dry Ice is non-toxic and does not contain harmful chemicals or pollutants, etc.        Dry Ice does not get stuck, attach to or lodge in the parts geometry or on the surfaces        Has ability to use micro-particle sized ice finish (e.g. clean, deburr, deflash, etc.) a wide range of parts, including parts that are micro sized and made with delicate materials.        Manipulation of parts and or delivery system permits focus to specific areas        Can be used as a cleaning operation to remove surface contamination or prep for secondary processesCons        Cannot be used to deburr/deflash parts in a batch        Burrs and flash can be difficult to remove when parts are at room temperature.        Operator dependent process that is inherently unrepeatable/programmable resulting in variable quality and results        Safety of the operator cannot be assured because parts and ice stream are not contained in an enclosure.It is to these shortcomings and “cons” in present day techniques that the present invention is directed to remedy.        